Ethanol Production Technology in Thailand

Asian J. Energy Environ., Vol. 3 Issues 1-2, (2002), pp. 27-51

Copyright © 2003 by the Joint Graduate School of Energy and Environment 27

Ethanol Production Technology in Thailand

Suthipong Sthiannopkao

Division of Environmental Technology

School of Energy and Materials

King Mongkut's University of Technology Thonburi

(Received : 10 April 2002 – Accepted : 10 October 2002)

Abstract : The use of ethanol as an alternative fuel source is presently

a worldwide topic of discussion and research. As once abundant

petroleum reserves dwindle and oil prices continue to rise, the search

for alternative fuels becomes more intensive. Nowhere is this topic

more relevant than Thailand, a country that imports 90% of the total

amount of petroleum used each year. There are many reasons for

Thailand to pursue an ethanol program designed to reduce dependence

on fossil fuels in the transportation sector. The potential positive

benefits of such a program for Thailand are well documented: relief of

trade balance burdens due to heavy reliance on foreign oil, use of a

potentially carbon neutral fuel, future national security, and rural

economic stimulus. Such incentives have recently encouraged

Thailand to consider ethanol production as a realistic opportunity to

accomplish these goals.

S. Sthiannopkao

28 Asian J. Energy Environ., Vol. 3, Issues 1-2, (2002), pp. 27-51

Keywords : Ethanol production, Alternative fuel, Fermentation,

Hydrolysis.

Production End

The face of ethanol production technology is old and ever

changing. It is widely noted that centuries ago man discovered and

began employing fermentation technology to produce alcohol; today

ethanol is produced from a variety of materials for use as an industrial

chemical and fuel. Through decades of research and development, the

production of fuel ethanol has been developing throughout the world.

Conventional processes have been maximized while advances

continue to be made in lignocellulosic biomass conversion. Tried and

true technologies such as acid and conventional enzymatic processes

have been built upon through greater discovery and understanding of

particular enzymes, advances in biotechnology and genetic

engineering, more effective plant designs, and so on. In this section

an attempt has been made to capture the essence of ethanol production

as it pertains to Thailand through a basic review of some ethanol

production processes including conventional technologies as well as

some of the notable advances in the technology.

Conventional Process

Thailand currently operates a number of pilot-scale ethanol

production facilities utilizing sugar cane or cassava feedstock. The


Asian J. Energy Environ., Vol. 3, Issues 1-2, (2002), pp. 27-51 29

description that follows serves only as a representative of variable

“conventional” fermentation-ethanol production processes. The

technology and techniques are here termed conventional in relation to

those some more advanced and less mature technologies and processes

discussed later. This base example will include some elementary

notes regarding ethanol production including the introduction of some

terms and processes that will be referred to throughout the section.

To begin with, any fermentation process producing ethanol via

fermentation requires a feedstock of some nature. Put simply, this

feedstock may be sugar, starch, or lignocellulosic in nature. The

feedstock must be pretreated and conditioned for fermentation

according to its particular composition. For a solid, this usually

includes some manner of grinding or chopping to produce very small

pieces of the feedstock. If the material is not already a saccharide, i.e.

starch, cellulose, or lignocellulose, it must then be hydrolyzed and

saccharified. A saccharide is defined as a simple sugar or a more

complex compound that can be hydrolyzed into simpler units.

(http://www.ott.doe.gov/biofuels/glossary.html) Starch is generally

defined as a polymer consisting of long chains of alpha-glucose

molecules linked together (Figure 1).

S. Sthiannopkao


The structure of starch tends to be amorphous and thus readily

hydrolyzed to the simpler glucose disaccharide, maltose.

Lignocellulosic material is more complex than starch. Such matter is

composed of three main components, namely cellulose, hemicellulose

and lignin. Generally the percentage composition of lignocellulosic

biomass is as follows: 40-60% cellulose, 20-40% hemicellulose, and

10-25% lignin, depending on the biomass. Cellulose is also a polymer

of glucose molecules, although linked in a different fashion. Units of

C6H10O5 are connected by β-glycosidic links that form linear and very

stable chains that exhibit extensive hydrogen bonding, and when

hydrolyzed split into the disaccharide celleboise (see Figure 2).

Figure 1. Structure of Starch (www.ott.doe.gov).



Figure 2. Structure of Cellulose (www.ott.doe.gov).

For these reasons cellulosic material is significantly more

resistant to hydrolysis than starchy material. Hemicellulose is a

branched heteropolymer of not just glucose, but multiple five and six

carbon sugars, such as the pentose sugars, D-xylose, L-aribinose, and

the hexose sugars, D-galactose, D-glucose, D-mannose, L-rhamnos,

and L-fuctose. The structure of hemicellulose varies with the

particular biomass, but generally xylose constitutes a relatively large

percent of the composition. Lignin is not composed of sugars, but is

instead a complex aromatic polymer. As such, lignin cannot be used

to make ethanol; however it can be utilized as a fuel source.

(http://www.ott.doe.gov/biofuels/glossary.html; Zaldivar, 2001)

The example of “conventional” technology provided here

illustrates the use of a solid starchy feedstock, such as corn. A basic

outline of the important steps in the process from raw feedstock to

ethanol is as follows:

S. Sthiannopkao


I. Transportation of the feedstock.

II. Storage of the feedstock.

III. Grinding or chopping, etc. of the feedstock.

IV. Hydrolysis of the feedstock by cooking with water and malt or

acid.

The prepared feedstock is cooked to gelatinize the material and

allow the malt or acid to break down the starch to fermentable

sugars. Generally well known enzymes, amylases, do the

work.

V. Growth of inoculating cultures of yeast or bacteria.

During the starch conversion yeast is grown in a separate tank

to be added to the fermentor along with the converted sugars.

VI. Fermentation.

The mash is fermented to beer with an alcohol content in the

range of approximately 6% by volume to up to approximately

12% by volume.

VII. Distillation from beer.

VIII. The fermented broth is passed through heat exchangers,

pumped to the top of a beer still, and as it passes down the

column it separates. In the end stillage, consisting of residual

sugar, protein, and maybe vitamins, leaves through the bottom

and alcohol, water, and aldehydes remain as the overhead. The



overhead is passed through heat exchangers and then on to a

dephlegmator. From here the condensate is sent to an

aldehyde, or head, column for the separation of low boiling

impurities.

IX. Rectification and purification of alcohol.

Finally, the alcohol is sent to the rectifying column where it is

raised to approximately 95%.

X. Recovery of byproducts of process.

As mentioned earlier, the stillage contains protein, residual

sugars, and possibly vitamins. This material may be dried and

used as animal feed or fertilizer. Carbon dioxide created may

also be sequestered and sold (Austin, 1984).

The above process serves as an appropriate foundation for the

presentation of the current technology used in Thailand to convert

cassava to ethanol. Fuel ethanol production in Thailand, although

poised for commercialization, is still limited to the pilot plant scale.

The Thailand Institute of Scientific and Technological Research

(TISTR), developed an effective cassava to ethanol pilot plant almost

twenty years ago. A recent visit to this particular plant indicated that

the technology has changed little, if any, since the plant’s construction

and implementation in the early 1980’s. The 1500 l/d capacity plant

was used to examine both conventional fermentation and distillation

processes, as well as a modified process that eliminates the cooking

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step during hydrolysis and employed a pressurized variation of

azeotropic distillation. Essentially the non-cooking hydrolysis is

achieved using the same amounts of α-amylase and glucoamylase

enzymes but allowing a longer reaction time. Together, these

modifications greatly reduce steam demand and thereby save energy

(Atthasampunna, 1987). Simpler still is the process for converting

molasses to ethanol (see Figure 3). As discussed later, Thailand has

abundant sugar cane, the processing of which results in molasses.

Molasses vary in grade depending on the level of processing from

which they result, but generally speaking molasses contain

approximately 50-70% carbohydrates (sugars). Final molasses result

when no more sugar can economically be removed and may contain

approximately 35% sucrose as well as various percentages of other

mixed sugars. Molasses can be fermented to alcohol using a

traditional yeast, such as Saccharomyces cerevisiae.



Traditionally fermented alcohol can be distilled to 90-95.6%

ethanol using a multi-column distillation process. The production of

anhydrous, or pure ethanol, 99-99.9% is accomplished by removing

the last 4-5% of water that remains. Various dehydration methods

exist, including traditional azeotropic, membrane technology, and

molecular sieve technology. Molecular sieves are crystalline metal

aluminosilicates and are essentially special filters, which, as the name

Figure 3. Ethanol from molasses (Scheitzer,1997).

S. Sthiannopkao


implies, work at the molecular level. When hydrous ethanol passes

through these special filters, the remaining water is adsorbed leaving

nearly pure anhydrous alcohol (Scheitzer, 1997). To date molecular

sieve technology is widely used and will be implemented at pilot

plants in Thailand and most likely at the commercial scale as well.

According to a personal communication with Khun Boonyipat (Nov.

2001), studies comparing the economics of differing distillation

methods at various scales of production, molecular sieve technology

seemed to be the most economical in terms of both investment cost as

well as operating cost.

A Brief Review

Within the entire ethanol production process, the areas of

greatest concern at present are the hydrolysis and fermentation steps.

These steps are the most expensive process steps yet offer the greatest

opportunity for cost reduction (Wyman, 1999). Furthermore, it is the

initial steps in production, the hydrolysis and fermentation technology

that dictates what feedstock may be used. For these reasons, the

technological advances presented in this section are primarily

concerned with these two areas of ethanol production. As described in

the sample process above, the feedstock, if not saccharine in nature,

must be saccharified.

Over recent decades intense research has been devoted to the

development of efficient, cost effective production of ethanol from



cellulosic biomass. The greatest hurdle to leap is the conversion of

such matter to fermentable sugars. The hydrolysis of cellulosic

material into its constituents may be achieved through a variety of

avenues. A 1994 report by the State of Hawaii includes a good

comparative review of some lignocellulosic conversion technologies.

This review has been used here to simply present the breadth of the

technology. The report is now of course somewhat dated, as the field

is ever changing, however for the purposes of this section the

information remains relevant. All the information refers to the

hydrolysis and fermentation steps of ethanol production. Traditional

fermentation receives the least attention as it represents the most

mature and well known process. The following brief descriptions

have been adapted from the 1994 Hawaii report, and each is

accompanied by a simple flow diagram.

Some hydrolysis processes utilize high heat and pressure to

disrupt the lignocellulosic material. The process described hereafter

was developed by Norval, in Canada. The biomass is prepared and

then forced through steam at high pressure into a flash/recovery tank.

When the pressure is decreased in this tank the auto hydrolysis of

hemicellulose material occurs, together with a slurry of cellulose,

hemicellolusic sugars, and melted lignin. The cellulose is then

available for conversion and fermentation, the hemicellulose for

fermentation, and the lignin for recovery (Figure 4).

S. Sthiannopkao


Figure 4. Steam disruption (Sheser,1994).

Another example employing an elevated temperature and

pressure process involves treating the lignocellulosic material with

acidified acetone at high temperature and pressure (see Figure 5).

Figure 5. Acidified acetone hydrolysis (Shleser, 1994).



In ammonia disruption, ammonia is infused via high pressure

treatment, causing the cellulose matter to swell and decrystalize.

Upon release of the pressure, the matter explodes into a recovery tank

where the cellulose and hemicellulose are readily converted to sugars

and consequently fermented separately by employing appropriate

yeasts (see Figure 6).

Figure 6. Ammonia hydrolysis (Shleser, 1994).

Some processes involve the use of acid to disrupt the

lignocellulosic matter. This acid can be utilized in either dilute or

concentrated forms to breakdown the biomass. The use of acid

processes maintain the longest history and are regarded as effective,

but in the past have not been economically viable except in specific

economic environments, such as times of war. Now certain advances

in the technology and processes have made acid hydrolysis processes

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more attractive by reducing costs and boasting little detrimental

environmental impact (Shleser, 1994).

Acid Hydrolysis Technology

Acid hydrolysis technology can trace its roots over a hundred

years. In these processes acid is used to condition the biomass such

that hemicellulose is converted to sugars and cellulose is susceptible

to conversion by appropriate enzymes. Dilute acid hydrolysis saw its

first attempt at commercialization in 1898 in Germany. The use of

dilute acid was adopted by the US from German technology and

through the years refined to an effective percolation process known as

the “Madison Wood Sugar” process. This process spawned even

further R & D and resulted in the development of dilute acid

percolation reactors that still find use in Russia. Concentrated acid

hydrolysis is nearly as old and has also been used commercially. The

Japanese used membrane technology in 1948 to separate acid and the

sugar, and during WWII, the USDA refined concentrated acid

technology at its Northern Regional Research Laboratory in Peoria,

Illinois. The process developed there, which came to be known as the

Peoria Process, received attention again in the 1980’s. Today

companies are attempting to refine these processes for increasingly

cost effective ethanol production by saving energy and limiting

environmental impact. However, acid technology is reaching the

limits of its potential after decades of development in greater sugar

yields and more efficient processes. Different companies boast



different concentrations of acid, different temperatures, different

durations of time, and so on with regards to the hydrolysis step.

Generally speaking however, dilute processes tend to require higher

temperatures than concentrated ones, and a greater amount of various

by-products result from dilute concentration schemes (DOE/biofuels).

The two examples provided here are based on technology developed

by Arkenol and BC International Corporation. Both of these

companies have developed advanced biomass to ethanol processes and

are poised to construct commercial plants or are engaged in

construction. Furthermore, both companies have expressed interest in

Thailand, however, no information seems to indicate any investment

in Thailand at this time.

Arkenol, a Nevada company based out of southern California,

operates a pilot scale plant near it’s corporate offices in Mission Viejo

and plans to build a commercial scale plant for the conversion of rice

straw. Because high concentration sulphuric acid is used, efficient

recycling is extremely important to Arkenol’s process. The company

breaks down the cellulosic material into it’s constituents, cellulose,

hemicellulose, and lignin. The cellulose and hemicellulose are

fermented separately and the lignin is removed to be utilized for fuel.

Arkenol terms the thermal requirements of the process as “moderate”

and seeks to build plants that use “waste” energy from power

producing facilities. The use of the ethanol plant as a “thermal host”

is one of the cost reducing factors that makes the overall process

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economically viable. One relative benefit of concentrated acid

technology is that there is relatively little degradation during the

conversion of the biomass to fermentable sugars (www.arkenol.com)

(see Figure 7).

BC International Corporation, a private company in Dedham,

Massachusetts, seeks to produce ethanol employing acid technology as

well, however employing a dilute acid process. In addition, the

company incorporates genetically engineered bacteria to ferment both

hexose and pentose sugars resulting from the hydrolysis of biomass

feedstock. The BCI process is founded upon the simplicity of

traditional starch fermentation as illustrated by the flow diagrams

below. The company hopes to shift to a fully enzymatic process, that

is enzymatic hydrolysis and simultaneous saccharification and co-

Figure 7. Arkenol flow diagram.



fermentation, once the technology matures and becomes commercially

viable (Gatto, 2000; www.bcintlcorp.com) (see Figure 8).

Figure 8. BCI simplified flow diagram (Gatto, 2000).

Another significant ethanol feedstock is municipal waste

(MSW). The conversion of this material to fermentable sugars can

also be achieved using acid technology. Masada Resource Group,

LCC operates facilities that produce fuel grade ethanol from MSW.

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Figure 9. A simplified illustration of the Masada technology/process

(http//:www.masada.com).

Waste is sorted, non feedstock material such as glass and plastic

are recycled, while lignocellulosic material and other biomass is

converted to fermentable sugars using acid hydrolysis technology. A

commercial facility was scheduled for full operation in Middletown,

New York in late 2001 or early 2002 (www.masada.com).



Enzyme Technology

The study of enzymes, often now referred to as cellulases,

responsible for the break down of cellulosic biomass was intensified

decades ago during WWII when the US army needed to understand

the deterioration of fabric in the tropical climate of the South Pacific.

The US Army Natick Laboratories were established in this effort to

understand and curb cellulose hydrolysis. As a result of these studies

the important cellulsase producing fungi Trichoderma viride, or as it

came to be known, Trichoderma reesei, was consequently discovered.

Cellulase research aimed at cellulose hydrolysis to achieve sugars for

food or energy came into being in the mid 1960’s when it was

recognized that the cellulase enzymes could be prepared from fungal

cultures. Such applications are still under intense research today as

scientists try to develop enzyme "producers" best suited to ethanol

production applications. Cellulase enzymes have been used in other

industries, where smaller quantities are necessary and the final product

is of greater value, such as stone washed denim (Sheenan, 1999). An

important breakthrough in ethanol production from cellulosic biomass

was the development of simultaneous saccharification and

fermentation, often designated SSF. This achievement was important

because it overcame a natural negative feedback mechanism in which

cellulose conversion to glucose is inhibited by the very glucose

produced. By saccharifying the cellulose and simultaneously

fermenting the glucose produced, this negative feedback mechanism

can be checked (Ingram, 1999). In addition, it literally can cut

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equipment costs in half by eliminating the need for separate

saccharification and fermentation vats associated with sequential

processes. Another significant area of development involves

microorganism engineering and development. As stated earlier, in

addtion to cellulose, lignocellulosic hydrolysis produces five and six

carbon sugars from hemicellulose, however, the traditional

microorganisms used for crop-based ethanol production from

fermentation, S. cervisiae and Z. mobilis, do not naturally metabolize

five carbon sugars (Zaldivar, 2001). Work in genetic engineering has

been and will continue to be the means to an end of the lignocellulose

to ethanol predicament. The characteristics described as essential for

enzyme producers are outlined below as adapted from Zaldivar,

Nielsen, and Olsson (2001).

I. Ability to utilize all the simple sugars derived from

lignocellulosic biomass.

II. Produce high ethanol yields and have high productivity.

III. Produce minimal fermentation by products such as

glycerol and succinate.

IV. Have relatively high or increased ethanol tolerance.

V. Tolerance to inhibitors resulting from chemical

pretreatment such as dilute acid hydrolysis.

VI. General hardiness and tolerance to fluctuations in process

conditions such as pH or salts (Zaldivar, 2001).

Scientists have been able to engineer bacteria and create

microorganisms which are “tailor-made” for producing ethanol from



complex biomass. In the US, National Renewable Energy Laboratory

(NREL) scientists have made progress in the development of highly

thermotolerant organisms as well as strains of xylose fermenting

Z. mobilis (http://www.nrel.gov/technologytransfer/licenselist.html

#biotech) Other genetically engineered organisms have the ability to

ferment all the five carbon sugars and others have been designed to

more efficiently convert and ferment cellulose. Ingram, et al (1999), at

the University of Florida have created two such designated GMO’s

KO11 and P2. KO11 is a particular strain of E. coli bacteria that has

been transformed using two specific genes from the bacteria Z.

mobilis. This microorganism is capable of converting all the pentose

and hexose sugars of hemicellulose. P2 was created from the bacteria

Klebseilla oxytoca by inserting the same PET operon as in KO11. K.

oxytoca naturally possesses the ability to ferment a wide range of

monomeric sugars while also being capable of metabolizing celloboise

and cellotroise, the products of enzymatic hydrolysis of cellulose. P2

is designed to convert cellulose and the resulting intermediates,

celloboise and cellotroise, thereby reducing the need for extra fungal

cellulases (Ingram, 1999). Enzyme technology and processes may be

the most lucrative area for research and development; when compared

to the other areas of ethanol technology, enzymes are the new frontier.

This area of research and development exhibits great potential for

further advances, and the cost reductions that can result from such

advances are significant. Sheenan and Himmel (1999) project savings

of $0.18 to $0.60 depending on the level of enzyme productivity and

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activity. The field of enzyme development has increased by leaps and

bounds in the past few decades, as has the field of biotechnology from

which these developments arise. The progress thus far seems to

indicate room for improvements and that these improvements are

forthcoming.

Conclusion

At present Thailand produces ethanol at the pilot plant scale

utilizing both cassava and sugar cane molasses. The technology

employed for this production is conventional and proven. There is no

doubt that in the near future Thailand can produce ethanol

commercially utilizing this technology, as it is already produced in

other parts of the world. At this time fuel ethanol production from

lignocellulosic biomass exists at the commercial scale although it is

not widespread, and not found in Thailand. Rather, existing

commercial facilities produce for the industrial alcohol market, which

is currently more lucrative. However, such technology seems to be

moving towards greater commercialization; the advances reviewed in

this section, particularly the progress in biotechnology, suggest the

large-scale production of competitively priced fuel ethanol from

various biomass sources is a real possibility in the near future. While

bioethanol production in developed countries requires crops grown

specifically for that purpose and substantial government subsidies,

Thailand has an abundance of agricultural residues, such as rice

hull/straw, sugar cane waste, cassava stalks, as well as feedstock



resulting from palm oil production and other biomass such as

municipal waste, which have encouraging potential for producing

ethanol. The key element being that residues and wastes are much

cheaper than crop-based feedstocks, and feedstock costs account for a

significant portion of total production costs. It is important to note

that many aspects must come together to make these technological

advances viable at the commercial scale. The information presented

here only shows the tip of the iceberg, and developments in processes

and materials exist in addition to the innovative hydrolysis and

saccharification advances. However, until these technologies become

more mature and increasingly economical it seems doubtful they will

find a place in Thailand.

References

[1] www.arkenol.com

[2] Atthasampunna, P.; Eur-aree, A. (1987) Utilization of Cassava

for Ethanol Production. In Upgrading of Cassava/Cassava

Wastes by Appropriate Biotechnology. Bangkok, Thailand.

[3] Austin, G. (1984) Fermentation Industries. In Shreeve's Chemical

Process Industries, J. Zseleczky (Ed.), 5th Edition, Mc Graw-Hill

International Editions, Singapore, 578-601.

[4] www.bcintlcorp.com

[5] http://www.ott.doe.gov/biofuels/glossary.html

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[6] Gatto, S. (2000) Ethanol From Biomass-The Next Generation.

Workshop on Biomass Derived Ethanol as Automotive Fuels in

Thailand, Bangkok, Thailand.

[7] Ingram. L. O. (1999) Enteric Bacterial Catalysts for Fuel Ethanol

Production. Biotechnology Progress, 15, 855-866.

[8] Mielenz, J. R. (2001) Ethanol production from biomass:

technology and commercialization status. Current Opinion in

Microbiology, 4, 324-329.

[9] Sheenan, J.; Himmel, M. (1999) Enzymes, Energy, and the

Environment: A Strategic Perspective on the U.S. Department of

Energy’s Research and Development Activities for Bioethanol.

Biotechnology Progress, 15, 817-827.

[10] Scheitzer P. A. (1997) Handbook of Separation Techniques for

Chemical Engineers. Mc Graw-Hill.

[11] Shleser, R. (1994) Ethanol Production in Hawaii. Prepared for

the State of Hawaii, Department of Business, Economic

Development and Tourism. Honolulu: Energy Division, Dept. of

Business, Economic Development and Tourism, State of Hawaii,

1. Energy crops-Hawaii. 2. Alcohol as fuel-Hawaii. 3. Biomass

energy-Hawaii. HD9502.5.B54.S4.

[12] Wyman, C. (1999) Biomass Ethanol: Technical Progress,

Opportunities, and Commercial Challenges. Annual Review of

Energy and the Envionment, 24, 189-226.



[13] Zaldivar, J.; Nielsen, J.; Olsson, L. (2001) Fuel ethanol

production from lignocellulose: a challenge for metabolic

engineering and process integration. Applied Microbiology and

Biotechnology, 56, 17-34.

Ethanol Production Technology in Thailand

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